Provided is a resin composition containing a resin component prepared by blending a graft copolymer with an engineering plastic, wherein the above graft copolymer is a graft copolymer satisfying (a) to (e) shown below: (a) a graft rate is 1 to 150% by mass, (b) a weight average molecular weight measured by GPC is 500 to 400000, (c) a molecular weight distribution (Mw/Mn) is 1.5 to 4, (d) a main chain is a polymerization chain containing 1 to 100% by mass of a monomer unit having a functional group interacting with the engineering plastic and (e) a side chain is a homopolymerization chain of a single kind selected from α-olefins having 3 to 28 carbon atoms or a copolymerization chain of two or more kinds selected therefrom or a copolymerization chain comprising an α-olefin unit having 3 to 28 carbon atoms and an ethylene unit which accounts for 50% by mass or less, and a mesopentad ratio [mmmm] of the polymerization chain is 30 to 80 mole %.